Exporting PME to wooden shed

[JohnW2]

...and, of course, all circuits being disconnected with a fault on one.

Well, yes, I was talking/thinking about the location of a single RCD (at one end or the other).

RCBOs are RCDs.

True, but since at least some of the circuits (maybe all) in the shed will need some sort of OPD, it would surely be best to use RCBOs if one wanted separate RCD functionality for each circuit.

Having said that, as you know, the most common arrangements one actually sees are (a) a mini-CU in outhouse, with a single RCD protecting all circuits or (b) fed from RCD-protected MCB in house CU (with the problems that brings) with an FCU for outhouse lights or (c) (probably the least sensible, but maybe the most common!) fed from RCD-protected MCB in house CU and with a mini-CU (with a single RCD) in outhouse. In all those cases, all outhouse circuits are protected by a single, common, RCD.

Kind Regards, John

 

[Notch7]

That's the approach which is 'undesirable' (albeit very common) - since in the event of a fault in the shed, it would be pot luck as to which (or both) RCDs would trip, and if it were the house one that tripped, it would take out a number of house circuits as well as the shed one.
Certainly at the house end but, sensibly, at both ends, since it then would considerably enhances the CPC/bonding connection to the shed.

Kind Regards, John

Many thanks -I wasnt sure if there was a technical reason for not have rcd twice on a circuit.

I suppose its natural to think rcd protection at house end would protect against fault occurance in cable.

I had read somewher the armour would only be connected at the house end, cant remember reason though

 

[JohnW2]

Many thanks -I wasnt sure if there was a technical reason for not have rcd twice on a circuit. I suppose its natural to think rcd protection at house end would protect against fault occurance in cable.[/quote]It would, but armoured cable does not need such protection.

I had read somewher the armour would only be connected at the house end, cant remember reason though

That's if you are NOT exporting the earth but, instead, are having a local TT rod as the earth at the outhouse. In that situation, the armour still needs to be 'earthed' at the house end, to protect it (so that an MCB or fuse in the house would operate if it were penetrated), but it is then essential that the armour is not connected to anything (or touchable) within the outhouse.

Kind Regards, John